1. Field of the Invention
The present invention relates to an additive for an acid electrolytic copper plating bath, a process for the preparation thereof and the copper electroplating of printed circuits therewith.
2. Description of the Prior Art
A wide variety of additive compositions for acid copper electroplating baths are of course well known to this art.
Thus, French Pat. No. 1,255,271 features acid copper electroplating baths containing one or more basic dyestuffs comprising, in particular, an ethenyl chromophore, amino compounds devoid of carbonyl groups, an organic sulfonic acid, or a water-soluble salt of such acid, which comprise at least one azido group in its molecule, as an additional brightener an organic compound having at least one carbon atom bonded exclusively to a hetero-atom, and which bears a hycrocarbon substituent bonded via a sulfur and/or nitrogen atom and having a hydrogen replaced by a sulfonic acid group, a thioamide or isothioamide which bears a sulfonic acid substituent bonded to the nitrogen atom of the thioamide or isothioamide group via a hydrocarbon radical, and a thiourea derivative in which at least one nitrogen atom is replaced by an alkyl or aryl radical bearing an ether, hydroxyl or carboxyl group.
Furthermore, according to Belgian Patent No. 572,186, acid copper electroplating baths are known which contain an amount of organic sulfonic acids, or the water-soluble salts thereof, which comprise at least one azido group in the molecule, an additional amount of sulfoalkyl esters of N-monosubstituted or N-disubstituted dithiocarbamic acids, or the water-soluble salts thereof, an additional amount of 1,3,5-triazine-2,4,6-tris-(mercaptoalkanesulfonic acids) or water-soluble salts thereof, and an additional amount of certain agents for improving the ductility of the coatings which result therefrom.
The particular additives described in the aforesaid patents are not satisfactory, however, notably because they degrade relatively rapidly during their use and their stability at temperatures above 25.degree. C. is low. Compare also U.S. Pat. Nos. 4,036,710, 4,036,711 and 4,038,161; Chemical Abstracts, 82, No. 26, p. 415, 177072u (June 30, 1975); Gerenrot et al, Zashch. Met., 11 (1), pp. 95-8 (1975).